The present invention relates to a technology for controlling a network synchronization device.
Up to now, there is a technology in which a multiplexer receives a clock from a master network synchronization device to maintain synchronization, and transmits data including clock information to another multiplexer through a data transmission line, and the another multiplexer extracts the clock from the data received through the data transmission line to maintain synchronization. In the above-mentioned configuration, when it is detected that a clock of the master network synchronization device has been interrupted, a remote alarm indication (RAI) signal is sent to the data transmission line, and when a slave network synchronization device receives the RAI signal, a clock of the slave network synchronization device is employed (Japanese Patent Laid-open Publication No. H11-205317).